The range operator is not going to help you much in this case (if you do not want to rely on indentation which I do not suggest). But you can simply count the depth of nesting the if's:
#!/usr/bin/perl

use warnings;
use strict;

my $depth;
while (<DATA>) {
    /#ifdef|#if|#ifndef/ and $depth++;
    print unless $depth;
    /#endif/ and $depth--; # this comes after the print not to be prin
+ted
}


__DATA__
{

 #if 1
  #define done 9
  #define do 10
  #ifdef
    #define def1 11
    #define thread 12
  #endif
  #define mutex 13
  #define inter 14 
 #endif
 #define intel 15
 #define intel_64 16
}

[download]

In reply to Re: nested #if directive matching matching by choroba
in thread nested #if directive matching matching by prassi

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.